Deep sea habitat with centuries-old marine life found off Ireland

Limid bivalves and deep-water oysters, together with corals located by NUI Galway scientists in a new deepwater habitat half a mile below sea surface in the Whittard canyon off the south coast. The photograph was taken by the NUI Galway team using a remotely operated vehicle deployed from RV Celtic Explorer

Marine scientists from NUI Galway (NUIG) have discovered a new deep-sea habitat off the southwest tip of Ireland which is rich in corals and unusually large and long-living oysters.

The habitat comprises a 150-metre vertical rock face carpeted in colonies of bivalves which may be up to 200 years old, about half a mile below the sea surface in the Whittard Canyon.

The canyon is one of a system and lies about 250km south-southwest of the coastline close to the limits between Irish and British waters.

Normally, life at such depths can be limited, but the scientists believe food particles carried by an internal wave, created by the canyon shape, may be sustaining a thriving community.

Dr Louise Allcock from NUIG’s Ryan Institute led the team which explored the canyon from the Marine Institute’s research ship, Celtic Explorer, using a remotely operated vehicle, Holland I.

NUIG marine environment Prof Mark Johnson said that it was very unusual so see “so many conspicuous animals so close together at these depths”.

The bivalves comprise yellow-brown large deep-sea oysters, classified as Neopycnodonte zibrowii, and spectacular orange-red-fleshed “limid bivalves”. They do not have a common name but are known to marine scientists by the Latin classification, Acesta excavata.

The details have been published today in the international academic journal PLOS ONE . “The bivalves are also remarkably large, and we know that deep-water oysters of this size elsewhere in European seas may be more than 200 years old,” Prof Johnson said.” “So we are probably seeing an exceptionally long-lived and stable community”.

A puzzle to the scientists is how the bivalves and corals survive at such depths, as they are filter feeders and rely on particles dervied from surface waters.

The team has studied the water column to determine how the “large and vibrant community” is getting its sustenance.

NUIG oceanographer Dr Martin Wall says there is evidence the “internal wave” in the canyon may be delivering food to the foot of the wall.

Remotely operated vehicles lowered from research ships have assisted in mapping deep sea habitats which can play an important role in recyling nutrients, in carbon sequestration and in serving as nursery areas for other species.

The State’s seabed mapping programme, Infomar, contributed to the new discoveries.

Howver, Dr Allcock says that the habitat is “potentially extremely vulnerable to damage” and measures would be required to protect it.

Such canyon systems are known to host organisms which can contribute to new pharmaceuticals – an aim of Ireland’s biodiscovery programme, as the NUIG team notes.